Alternating-current-distributing system.



S. D. SPRONG & W. E. MCCOY. ALT'ERNATING CURRENT DISTRIBUTING SYSTEM. APPLICATION FILED 0GT.16, 1911.

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Patented Aug". 13, 1912.

UNITED STATES PATENT OFFICE.

SEVERN D. STRONG AND WALTER E. MCCOY, 0F NE? YQRK, N. "L, ASSIGNOR-S OF ON THIRD TOFRANK 7. SMITH, OF NEW YORK, N. Y.

'ALTERNATING-CURRENT-DTSTRIBUTIN G SYSTEM.

Specification of Letters Patent.

Application filed October is, 1911f Patented Aug. 13, 1912. Serial No. 654,909.

To all whom it may concern:

Be'it known that we, SEVERN D. SPRONG and (ALTER E. MoCoY, citizens of the United States, residing at New York, in the county of New York and State ofv New York, have invented a certain new and'nseful Improvement in Alternating Current Distributing Systems, of which the following is a specification.

In alternating current distribution sys 'tems in order to obtain a betterregulation at the customers premises and to take advantage of the diversity factor in the various customers demands, it has been found desirable to provide secondarymains supplied by comparatively few and large transformers. pacity is then less than in the .,case Where each customer is supplied by'a separate transformer, because the maximum demand of all thejcnstomers supplied from the secondarymain does not occur at the same instant. This secondary system is objectionable for the reason that in case a transformer burns out or becomes short circuited, there is a reverse flow of currentfrom the secondary mains into the short-cireuited transformer; the energy coming from the other transformer thus eliminatedis'thrown on transformers connected in multiple. The proportion'of the normal loadborne by the the remaining transformers, and, in addition, as the transformer is short-circuited and becomes a heavy demand in itself, this excess load is also thrown on the remaining transformers. There is, of course, a fuse between the secondary of the. transformer and the secondary main of a capacity equal to the maximum output of the transformer. Therefore it is seen that the cnrrentthat can flow in the reverse direction from the secondary into the defective transformer must equal the rating of the fuse before the defective transformer will become isolated by the blowing of its secondary fuse. It follows from this condition that the remainingtransformers have not only to carry their normal load, but in addition their proportion of the normal load otherwise supplied by the defective transformenhnd also must supply enoughenergy to blow the fuse.

of the efective transformerso as to eliminate it from the secondary system. Where a large number of transformers 1s used, the

The aggregate transforming ca-' relatively small, but'in practice the loss or drop in voltage inqthe secondary main. is so considerable that the transformer nearest the one that is defective is called upon to carry much. the larger proportion of the load, whichin turn causes it toblow out its fuse, thus shifting the heaviest-portion with a similar result; so that in the end, all the-transformers become disconnected in.

turn, due to overload. Y

Our present invention overcomes this difiiculty.

It is illustrated in the accompanying drawing, which is an electrical diagram. showing two sets of apparatus, connected to primary andsecondary, mains, the said sets beingalikeQso that a description of one set will serve. forjboth.

"Similar numbers and letters of reference indicate like parts.

It may be assumed that the potential on the primarymains 1, 2 is 2200 volts, which is stepped downby the transformers A, B to 110 volts on the secondary mains 3, 4, towhich'secondary mains are connected the load circuits 5. On the step-down transformer A is a primary coil C, and secondary c'oil D. I

Associated with each step-down transformer is a current transformer E, having three coils ,F, G, H. The terminals of coil F, which is of few turns and therefore of low voltage and high current capacity, are connected to the end terminals 6, 7 of a loop fuse J. The terminals of coil G are connected respectively to secondary main 3. and to terminal 6 of fuse J. vThe terminals of coil H are connected respectively to primary main-2, and one terminal of primary coil 0 on transformer A. The terminals of the secondary coil D on transformer A are connected to an intermediate terminal 8 on fuse J, and to secondary main 4. The coils G, H on transformer E have a -ratio of ampere turnssimilar to that of coils D. C on transformer A, and are of opposite polarities, so that normally they neutralize one another, and induce no current on the third coil F.

The leads are asfollows: from primary main 1, through primary coil C of stepdown transformer A, to coil H of transextra load thrown on each one would be of the load to the next nearest transformer lOO former E, to primary main 2, the usual fuses K being interposed; from secondary main 4, through fuse L, to secondary coil In event of a transformer becoming shortclrcuited or burned out, the current coming on the secondary mains 3,4, from the other transformers of the system, flows from said mains in the reverse direction to coil G. This reverses the polarity of said coil, and

, puts it in serieswith coil H so far as the energizing effect of said coils on the core of transformer E is concerned. ,A high amperage current isthen induced in coil F which burns out fuse J, which is suitably proportionedfor this result. This breaks the secondary circuit of transformer A, and so eliminates .that transformer from the system. In other words, the third coil- F on transformer E is normally short-circu'ited byfuse J, which fuse is also over a portion of its length in the secondary circuit of the step-down transformer A. When transformer A is short-circuited within itself, then the reverse current from the secondary main causes coils G, H, which hitherto neutralized one anothers effect on coil F, to unite said effects, and induce in coil F a current strong enough to blow fuse J, and so interrupt the secondary circuit of transformer A and so cut thattransformer out. of the system. 'Obviously, this can be accomplished only by the reversal of the current from the secondary mains. It is to be noted that when the loop fuse J is blown, both branches of the fuse are interrupted, so that connection is broken from middle fuse terminal 8, through one branch,

to secondary main 3, and through the other branch, to coil F; also that in accomplishshall not be blown simultaneously.

ingfhe present purpose, we eliminate'all movingparts, such as switches, relays, etc. It is preferable to place the branches of the fuse J sufficiently near together to cause rupture of one branch by the blowing of the other, in case for any cause both branches We claim:

1. An alternating current distributing system, comprising primary and secondary mains, means for establishing a current on said secondary mains, two transformers interposed between said mains, one of said transformers having three coils, two of said coils being of opposite polarity and mutually neutralizing one another and respectively connected in series with'the primary and secondary coils ofthe other transformer, and afuse connected at one end to one of said last-named ,coils, at an intermediate point to a secondary terminal of the other transformer, and at both ends to the terminals of said third coil.

2. An alternating .current distributing system, comprising primary and secondary mains, means for establishing a current on said secondary mains, a step-down transformer interposed between said primary and secondary mains, a current transformer having three coils, two of said coils being re spectively interposed in the primary and.

secondary circuits of said step-down transformer 'and of opposite polarity mutually to neutralize one another, and a fuse short-circuiting the third coil and having a portion of its length between said third coil terminals included in'the secondary circuit of said step-down transformer.

In testimony whereof we have affixed our signatures in presence of two witnesses. SEVERN D. SPRONG. WALTER E. MCCOY.

Witnesses:

GERTRUDE T. PORTER, MAY T. MoGARnY.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents. Washington, I). C." 

